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* ''Manga/The100GirlfriendsWhoReallyReallyReallyReallyReallyLoveYou'': On the surface, Kishika Torotoro is the responsible and knightly third year captain of the school kendo club; however, her responsibilities growing up starved her of the chance to enjoy being a kid, which resulted in a secret desire to be pampered, mentally regressing to an infantile state whenever someone indulges her desire.
* ''Manga/AfterGod'': Obikawa is irritated by "intellectual" topics, likes to pester people to act in the way he wants, and is generally impatient. [[spoiler:Him being the Snake IPO explains him not being familiar with social norms, but even after being exposed, he's still bratty and likes games.]]
* Aoi from ''Manga/AoiDestruction'' is 38 but [[OlderThanTheyLook looks]] prepubescent and acts like an elementary schooler.
* {{Discussed}} in ''Manga/AsteroidInLove''. When [[TheProtagonist Mira]] shows she is [[FriendToAllChildren very good with children]], Yuu wondered alound whether that's because she's "more similar to a child", given her {{cheerful|child}} [[TheDitz ditz]] demeanour is rather child-like. Chika immediately shuts [[InnocentlyInsensitive Yuu]] up (again).
* ''Manga/AzumangaDaioh'': Yukari Tanizaki is rather immature [[SenseiChan despite being the main characters' teacher]], which is lampshaded by her students and her fellow teachers. She tends to throw tantrums or sulk like a little kid when things don't go her way; she has been known to [[ApatheticTeacher get bored enough with her own classes]] to ditch them to go swimming or rope her students into playing sports instead. At one point, she arrives late to class because she was stuck in line to buy a Platform/PlayStation game. To top it all off, she is unmarried and still lives with her parents.
* ''Manga/{{Bleach}}'':
** Unohana compares Kenpachi to a child when he [[spoiler:screams at her not to die after killing her, [[LonelyAtTheTop saddened that they won't be able to fight anymore]]]].
** As if to play on the above, the [[AdaptationExpansion anime adaptation]] of Kenpachi's fight with [[ImaginationBasedSuperpower Gremmy]] has the former visually regress to [[BloodKnight a smiling child]] when he [[spoiler:cuts down [[MeteorSummoningAttack the meteor Gremmy just summoned]] after releasing his Shikai]].
* ''Manga/CellsNotAtWork'': Instead of the young children seen in the main series, the Erythroblasts of ''NOT at Work'' are a group of immature young adults that still live at their nursery.
* ''Manga/CityHunter'': Ryo's emotional maturity outside of work is questionable at best, especially with how much of a lech he is. Although considering how utterly ''[[ChildSoldier FUCKED]]'' [[DarkAndTroubledPast his childhood was]], it’s somewhat understandable.
* ''Manga/{{Claymore}}'' has one of the few, female examples. The warrior Helen is more often childish. She likes and teases other warriors or provokes them for fun. She was so annoyed by Clare that she said Raki would be her "nocturnal toy". Later in the manga you can see her celebrate with other warriors and, although all the warriors can control whether they let alcohol come to them, Helen is the only one who drinks without restraint because she enjoys it.
* ''Manga/DeathNote'':
** L sits like a kid, eats a lot of sugar, plays with his food, and in the anime, after hearing something important, ran and dove headfirst on the couch like a ten-year-old boy would.
*** They give the reason for his sitting position being that the brain gets the most oxygen from that posture. His liking of sugary foods has been explained in special material as being necessary for his brain, which burns calories like mad. [[ShownTheirWork Brains do consume a large number of calories and given L's job, his must be working around the clock.]]
** Near. He's 17-18 in the post-timeskip (21 in the post-series one shot) and he's always seen playing with toys.
* ''Anime/DigimonTamers'': Growmon/[[DubNameChange Growlmon]] is just a larger (though notably shorter than [[Anime/DigimonAdventure Greymon]]) Guilmon. Growlmon is mentally slightly older, but he carries most of Guilmon's childish personality. Averted with Wargrowlmon, who is pretty snarky and serious.
* ''Franchise/DragonBall'':
** When there isn't something to punch, [[TheHero Goku]] embodies this trope, often acting less mature than his '''granddaughter'''. ''[[Anime/DragonBallSuper Super]]'' really [[{{Flanderization}} plays this aspect up]] by making him whine about not training and him having petty rivalries with [[TheRival Vegeta]] like who can cut grass the fastest.
** The [[QuirkyMiniBossSquad Ginyu Force]] would qualify, playing jan-ken-pon to see who gets to fight who, and betting chocolate bars on the outcome of fights.
** The future variant of [[{{Cyborg}} Android 17]], in all his fascination with his own personal entertainment, is the kind of PsychopathicManchild that borders on this trope.
** Fat Buu once he turns good and becomes [[LiteralSplitPersonality Good Buu]]. He no longer devours people and is overall a nice guy. Doesn't stop him from throwing tantrums when he wants to eat and refusing to share his food with others, something that gets him in trouble with Beerus. It was also his innocence that allowed Babidi and his father to take advantage of him.
** [[Anime/DragonBallSuperBroly Broly]] is a tragic example as while he’s more polite and far less battle hungry than Goku and Vegeta (whom he is the same age as), due living decades on Vampa, Broly has got the mind of [[WildMan a wild child]]. He tries to eat snacks with the wrappers on before Cheelai stops him, and Broly still wears the ear of an alien he befriended as a child. [[spoiler: Broly also freaks out at the death of his father Paragus the same way a small child would, albeit with more destructive results]].
* ''Anime/{{FLCL}}'': Amarao is a subtle example, [[EstablishingCharacterMoment established early on]] when it's revealed that he has a serious SweetTooth and hates spicy food ("spicy = adult and sweet = kiddy" being a recurring motif in the series.) He spends his whole time in the series trying to turn Naota away from his ComingOfAgeStory CharacterDevelopment, and WordOfGod confirms that he's basically an older version of Naota without said CharacterDevelopment.
** Many of the adults in the series [[AdultsAreUseless are irresponsible and/or immature]], though Naoto's dad Kamon Nandaba stands out the most. Who gets jealous of their own kid getting into a relationship with a girl?
* ''Manga/FoodWars'': Asahi Saiba, the main antagonist of the final arc, has many tendencies like this. For starters, he holds an IrrationalHatred for protagonist [[TheHero Soma Yukihira]], simply because he's the biological son of his mentor Joichiro (Soma's mother had recently passed and he had to go back home to raise him). When first introduced, he's shown trying to court Erina Nakiri but drives her away with his advances, not realizing how toxic they are, and resorts to ''kidnap'' her and practically blackmail her into competing with him [[AndNowYouMustMarryMe to force her to marry him]] (and at the time, unaware that [[SurpriseIncest she was his half-sister]]). Growing up with [[AbusiveParents an abusive alcoholic mother]] gave the guy serious issues and much of his actions are motivated for a desire [[IJustWantToBeLoved to have a family who loves him]].
* Milla Ackerman from ''Anime/{{Godannar}}'' before regaining her full memories.
* A female variant is the high elf archer from ''Literature/GoblinSlayer''. She is quickly excitable, makes fun of others and generally behaves childishly. She is also idealistic to the point of naivety. Since she lives in a [[DarkFantasy brutal world]], she is inevitably becoming more serious in some episodes.
* ''Manga/HayateTheCombatButler'':
** How an irresponsible and immature drunk like Yukiji Katsura, Hina's older sister, hasn't been fired from her job as a teacher is beyond any conceivable logic, but luckily for her [[GagSeries logic doesn't apply here]]. Case in point: the superintendent is far crazier.
** Hayate's parents probably qualify too, since they don't seem to even realize how their horribly selfish actions affect other people, especially Hayate.
* ''Webcomic/HetaliaAxisPowers'':
** Yes, new viewers, the character throwing a tantrum and beating a dragon with a Franchise/HelloKitty doll is a ''[[ReallySevenHundredYearsOld four-thousand-year-old]] [[DudeLooksLikeALady man]].''[[note]]Referring, of course, to [[ImmortalImmaturity China.]][[/note]]
** There's also America, who acts like an [[LargeHam overexcitable and loud]] LoveFreak teenager at most, to say nothing of his tendency to [[SelectiveObliviousness step on others' toes]] and his AttentionWhore attitude. [[FridgeBrilliance However, this could be a clever nod to the USA's relative youngness (being under 250 years) compared to many other nation states in the world, with some around for centuries or even millennia.]]
** Russia started out as a creepy, pretty threatening PsychopathicManchild, but as his cutesy, giggly and more harmless traits were emphasized, he became LighterAndSofter.
** Poland had a ''strong'' attitude of ItsAllAboutMe early on, with his tendency to [[WithFriendsLikeThese push and drag around his best friend Lithuania]], though with CharacterDevelopment he becomes less selfish and much more patient.
* Rino Juse from ''Manga/ICantUnderstandWhatMyHusbandIsSaying'' whines and flails her arms like a little kid when complaining about things she doesn't like, [[ParentingTheHusband her husband Nozomu views her more as his child than his wife]], and she likes omelet rice (which is [[AgeStereotypicalFood often viewed as a kid's meal]]).
* ''Manga/{{Inuyasha}}''
** Inuyasha looks like a 15-year-old boy, but he's more than 200 years old. However, he does not show a trace of maturity and sometimes behaves like a child. Even Shippo, who is himself a child, feels sometimes annoyed by this.
** ''Anime/YashahimePrincessHalfDemon'': The sequel series has Moroha. Obviously the apple didn't fall far from the tree, because for a girl of fourteen, Moroha behaves very childishly.
* Usagi from ''Manga/JunjouRomantica'' appears to be this. He's actually trying to simulate a child's environment because he wanted to "recreate what normal kids do in their childhood".
* Apachai Hopachai in ''Manga/KenichiTheMightiestDisciple'' is known as the "Death God of the Muay Thai Underground" and is a deadly fighter in combat. Outside combat, however, he's very innocent, gentle, and childlike.
* King Dedede in ''Anime/KirbyRightBackAtYa'', he tends to act childish, constantly whines and demands his way and orders monster to sick on the Cappy's and Kirby ForTheEvulz.
* Ryotsu of ''Manga/{{Kochikame}}'' shows shades of this. He still rides a bicycle, likes things like video games and model kits, enjoys pulling pranks on people and generally acts immature most of the time. He can be competent if the situation calls for it, but that isn't often.
* ''Manga/LifeWithAnOrdinaryGuyWhoReincarnatedIntoATotalFantasyKnockout'':
** Tachibana is thirty-two years old, but his personality better fits the younger body he's transformed into. He rarely plans anything ahead, throws tantrums when he can't get his way, and is heavily reliant on Jinguuji to take care of everyday tasks.
** Although much higher-functioning, Jinguuji is NotSoAboveItAll himself. His social skills only hold so long as he believes others are treating him fairly, otherwise Jinguuji shows himself to be very short-tempered, selfish, and impatient.
* Deconstructed with Ilulu from ''Manga/MissKobayashisDragonMaid''. She lost her parents at a young age which, combined with being raised to be an AxCrazy Chaos Dragon afterwards, left her emotionally stunted. She is shown to identify with children more than adults post-HeelFaceTurn despite being the same age as Tohru. Scenes featuring Ilulu, but not focusing on her, often treat her no differently than Kanna, an actual dragon child who attends elementary school, and Kanna's human friends, also elementary schoolers.
* Skadi Dragenfelt in ''Literature/MonsterGirlDoctor'', [[spoiler:after having the parasitic growth on her removed]], is shown act just as childish as she looks, whether it's enjoying being pampered and hugged or [[spoiler:referring to Glenn as "big brother" and teasing him about whether or not he finds her attractive]], even though she's the chairwoman of the town and is nearly a thousand years old.
* Papi from ''Manga/MonsterMusume'' looks and acts childish, gets easily confused, forgets things immediately, and loves playing video games. She also is shown to identify with children more than adults despite being as old as Miia.
* Tomura Shigaraki/[[spoiler:Tenko Shimura]], the main antagonist of ''Manga/MyHeroAcademia'', is a twenty-year-old PsychopathicManchild who often describes things in video game metaphors and is motivated by a childish, shortsighted desire for revenge against the whole world. However, it's revealed that [[spoiler:his father, Kotarou Shimura, [[AbusiveParents abused Tenko due to the boy's interest in heroes]], and that when Tenko's quirk [[DisintegratorRay Decay]] manifested, it ran out of control and killed his dog, sister, mother, maternal grandparents, and eventually father. Afterward, Tenko was found by [[BigBad All For One]], who took him in and raised him as a successor, [[JustifiedTrope encouraging his hatred of everything in order to make him the ideal person to bring down hero society]].]]
* Catarina in ''Literature/MyNextLifeAsAVillainessAllRoutesLeadToDoom'' is a bit of an odd example since she's physically only 8-16 depending on where in the story you are. However, since she remembers the entirety of her seventeen years of living in her past life, she considers herself to ''actually'' be 25-34. And yet she still behaves like a hyperactive six year old half the time. Brain damage may or may not be to blame.
* ''Manga/MyRoommateIsACat'': Kawase shows a lot of childlike enthusiasm for his age and is generally oblivious to the fact that his friend's cat doesn't like him because he's too noisy and overbearing. Unsurprisingly, when children end up being in said friend's house at the same time as him, Kawase joins their games without a second thought and gets along with them swimmingly.
* Misato from ''Anime/NeonGenesisEvangelion''. {{Downplayed|Trope}}, and [[BrokenBird played for tragedy]] instead of humour. Her flighty, immature behavior when she's not on duty (which is reminiscent of someone who never grew out of their wild college years) is a cover for serious emotional issues, and hinders her ability to connect to her wards and pilots, Shinji and Asuka.
* Luffy from ''Manga/OnePiece'' is either one of the top codifiers of this trope or a [[DitzyGenius Ditzy Genius]] with a playful way of approaching things. Either way, the guy is an infant trapped in a young adult's body, always thinking about the most childish things and having no mature aspects outside of fighting and being a beacon of [[HeroicWillpower Heroic Determination]] for the crew and his allies.
** Speaking of the crew, there are many manchildren onboard: Usopp is as childish and stubborn as Luffy is, and WordOfGod is a bad influence on his own captain. Franky is in 30s but wears no pants, plays games, and is as silly as younger crewmates while still remaining TeamDad. Brook is 99-years-old, but has been a goofball all his life and beyond [[TheUndead as a living skeleton]]. Sanji seems very mature at times, but frequently proves to be a silly [[LovableSexManiac girl-crazy]] ManChild whose behaviour has been present since he was [[DirtyKid 9-years-old]]. Zoro almost averts this, as unlike previous examples, he remains stoically mature and ComicallySerious nearly all time... except when [[VitriolicBestBuds interacting]] with aforementioned Sanji, as Zoro proves to be a childish, petty, competitive Man Child when bickering with the cook.
** On a darker note, Boa Hancock is a WomanChild. She is one of the strongest females around and one of the Seven Warlords. However, when around Luffy, she acts much like a preteen girl in love and disregarding that, can act like a sulky teenager when it comes to her mother figure and demanding as a queen. [[JustifiedTrope Painfully justified by the fact her and her sisters were traumatized by their years of slavery and for Hancock, the experience utterly stunted her development growth.]] Her sisters are more mature, but they still show their PTSD in different ways.
** On an ever darker note, there’s Charlotte Lilin, who is an 68-years-old woman along with being an Emperor of the Sea. She also has 85 children and is a complete [[PsychopathicManchild Psychopathic Womanchild]] who hungers for sweets and goes on an UnstoppableRage whenever she doesn’t get what she wants. [[spoiler: It becomes more tragic as we learn from her DarkAndTroubledPast that her behaviour at age 5 wasn’t much different than she is now; she was just poorly raised and EasilyForgiven for her violent actions, which turned Linlin from a sweet girl to a violent Pirate]].
* Doctor Tokita in ''Anime/{{Paprika}}''. His workplace has action figures all over the place, he wears t-shirts for the amusement park he went to as a kid and he tends to get too wrapped up in the [[RuleOfCool cool-factor]] of whatever he makes to consider the actual ramifications. He’s a pretty decent guy though.
* ''Anime/PokemonTheSeries'':
** Jessie is in her mid-20s, but she is extremely immature. She's prone to having hissy fits and even lashes out at James and Meowth when they say and do things that she doesn't agree with. Ash and his friends are much more mature than her.
** Brock's MissingMom Lola was immature and flighty to the point that she walked out on her family for years on a whim with his dad Flint being too much of a HenpeckedHusband to fight her on it, before returning to the Gym like nothing happened.
** In ''Anime/PokemonTheSeriesSunAndMoon'' in a case of AdaptationPersonalityChange, Lusamine is an immature Woman Child and an AmazinglyEmbarrassingParent to her daughter Lillie, giving her own daughter a noogie and acting more like a big sister than a mother. Lusamine even has a thing for {{sentai}}. This gets [[PsychopathicManchild exaggerated]] when she [[spoiler:fuses with Nihilego]]. In contrast, her daughter is an AdorablyPrecociousChild.
* ''Manga/RanmaOneHalf'':
** Hinako Ninomiya is somewhere in her mid-to-late twenties; however, thanks to [[OldMaster Happosai]], her body ages incredibly slowly, so she currently looks like a ten year-old girl. She can only grow up to reflect her true age by absorbing the BattleAura of highly-combative people around her, and even then, only temporarily. How she acts depends entirely on how she ''looks'' -- she could be watching ''Manga/{{Doraemon}}'', reading Shojo or gushing over the giant panda in the living room as a child one second, only to suck out Ranma's [[BattleAura ki]] and try to hook up with Akane's father as a grown, mature woman the next.
** Happosai's general outlook on life can be summarized roughly as "five year old child with the hormones of a [[AllMenArePerverts stereotypical boy]] just hitting puberty".
* ''Literature/ReZero'' shows the half-elf Emilia. She is older than Subaru chronologically and physically, but she is much younger emotionally. She is so inexperienced and innocent that she even believes that kissing can make you pregnant.
* Atsushi in ''Manga/RecorderAndRandsell'' is an unusual variant -- he really ''is'' a child, but looks like a grown man.
* ''Anime/SailorMoon'': Despite being a SternTeacher, Miss Haruna is often shown to be [[SenseiChan just as immature as Usagi and her friends]], as she is consistently shown to be boy-crazy and even wears GoofyPrintUnderwear as seen in one episode.
* Galactic ''otaku'' Sergeant Keroro of ''Manga/SgtFrog'' is this. He followed Pekopon anime as a child, then was subjected to TrainingFromHell until he was assigned to Pekopon to lead the invasion... making it far easier to follow his old hobbies as a result. Just picking up where he left off in life.
* Naki from ''Manga/TokyoGhoul''. Emotionally immature, easily confused, and surprisingly childlike when he isn't being [[PsychopathicManchild psychopathic]]. He frequently misunderstands conversations, is prone to screaming/crying meltdowns, and at one point proudly explains that he is writing a letter to his beloved CoolBigBro in Heaven.....and it will be delivered as long as he addresses it to "Heaven". While an antagonist, he is portrayed as one of the most sympathetic characters due to his childlike nature.
* ''Manga/{{Trigun}}'':
** Vash the Stampede is a donut-loving goofball who frequently plays with groups of children, chases girls and in general loathes violence. [[spoiler:This doubly ironic since he's actually a 131-year-old [[HumanAliens Humanoid Plant]] who has a genius-level IQ, though Vash is technically ObfuscatingStupidity a lot of the time]].
** Milly Thompson is prime female example, being a 5'10-inch-grown Womanchild who easily gets upset over things such as pudding and is almost painfully naive at times. With that said, being so innocent, she's one of the few people who can get away with giving AllLovingHero Vash a slap when he steps out of line.
* The title character of ''Manga/TonariNoSekiKun''. A high-schooler with [[MrImagination a lot of imagination]], who spends all of his school time playing with various toys, or doing other things that have nothing to do with schoolwork.
* ''Manga/{{Yotsuba}}'' has Yanda. The chapter introducing him shows him having petty arguments with the 5 year old Yotsuba, aiming childish insults at her, and [[EnemyEatsYourLunch taking a big bite out of her ice cream]]. This and later chapters portray him as a major moocher when it comes to food and vacation time, and the chapter where he tags along on a trip to a ranch shows him to be just as easily amused by the animals there as Yotsuba. This is all despite the fact that he's a grown man and the coworker of Yotsuba's dad.
* ''Franchise/YuGiOh''
** [[ScrewTheRulesIHaveMoney Pegasus J. Crawford]]/Maximillian Pegasus from ''Manga/YuGiOh'' despite being YoungerThanHeLooks is a large fan of cartoons, talking about them fondly in his youth to Kaiba and vividly recalling all the episodes. This led to him using a Toon deck, though being the creator of the game, he gave his Toon monsters effects based on ToonPhysics, making them near ''unstoppable'' in the anime and while they were nerfed for the actual card game (and later episodes), they are still a serious contender. That being said, Pegasus has also his serious and dark side, which is reflected by some of his other cards, especially [[EldritchAbomination Relinqueshed and Thousand-Eyes Restrict]].
** ''Anime/YuGiOh'': [[Characters/YuGiOhSetoKaiba Seto Kaiba]] can fall into this through obsessing over being the best at games like Duel Monsters, bullying and talking down to people particularly Jonouchi, refusing to move on from the past until he delivers a defeat to his enemies to satisfy his lust for power and his reputation, and he also has childish arrogance of where he frequently boasts about his successes saying that he never needed help from anyone and doesn't rely on anyone to succeed even though he gets help from people all the time like Mokuba and his [=KaibaCorp=] employees.
* ''Manga/ZettaiNiFuroNiHairitakunaiKanojoVsZettaiNiFuroNiIretaiKareshi'': The title translates to ''Girlfriend Who Absolutely Doesn't Want to Take a Bath VS Boyfriend Who Absolutely Wants Her to Take a Bath'' and, just as that suggests, the girlfriend Hina is constantly opposed to taking baths, necessitating her boyfriend Teppei finding ways to cajole, trick, or bribe her into it much like an uncooperative child. Hina would just rather play games, watch videos, or otherwise laze about. Specific examples include distracting Hina with a game of shiratori, bathing her as she's distracted struggling to come up with a long phrase due to a rule they added, or turning the bath into a pretend pool to beat the heat.
* In ''Manga/Zom100BucketListOfTheDead'', Akira is determined to live life to the fullest now that he's freed of his abusive job, indulging all of his hobbies as he and Kencho scratch things off their bucket list. This also means they get outrageously excited over silly things that fly in the face of logic when it comes to survival, such as acting as superheroes or building a treehouse. Unfortunately, their shouting also tends to attract the zombies, much to Shizuka's chagrin.
* Tae from ''Anime/ZombieLandSaga'' is an interesting variant. As time goes on, she goes from being mindless to demonstrating curiosity and interest in the world around her, albeit in a very basic manner. In essence, being a woman child is a step ''up'' for her.
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